The above mentioned clamp device is used for interconnecting piping components in an exhaust system for an automotive engine, as an example (inter alia piping components for a turbo-charger). Several pertinent techniques have so far been applied for patent or utility model. Examples of these techniques include ‘Clamp for supercharger’ disclosed in Patent Literature 1, ‘Fixed bolt type coupling’ disclosed in Patent Literature 2 and ‘Ring-shaped clamp’ disclosed in Patent Literature 3. In particular, the basic structure of the ring-shaped clamp, disclosed in Patent Literature 3, is rather similar to the structure of the clamp device which is indicated herein in FIG. 1 to FIG. 3 and which is referred to herein as Comparative Example (Related Art Example). In the following, the clamp device (Comparative Example) shown herein in FIG. 1 to FIG. 3 will be illustrated in place of discussing the related art technique.
Referring to FIG. 1 to FIG. 3, the clamp device, the present invention is to be compared to, includes a main clamp body 10, a connecting ring 21, a bolt 22 and a nut 23. The main clamp body 10 is made up by upper and lower pair clamp members 11, 12. The upper clamp member 11, that is, a first clamp member, and the lower clamp member 12, that is, a second clamp member, are semi-arcuately shaped. Each of the first and second clamp members has its inner rim side formed with an elongated tightening groove 13 having a U- or V-shaped transverse cross-section. Each of the first and second clamp members 11, 12 includes a curled part 14 at its one end, while including a lobe part 15 at its opposite end. The curled part 14 of the first clamp member 11 and the curled part 14 of the second clamp member 12 are interconnected by the connecting ring 21, so that the two clamp members 11, 12 may be rotated relative to one another, that is, moved in a opening or closing direction, about a site of the interconnection as the center of rotation. With the lobe part 15 of the first clamp member 11 (first lobe part) located in a facing relationship and in proximity to the lobe part 15 of the second clamp member 12 (second lobe part), the clamp body 10, made up by the two clamp members, presents a C-shape when viewed from the front side. In this Comparative Example, the bolt 22 has its head welded to the first lobe part, while having its shank passed through a through-hole, not shown, bored in the second lobe part. The nut 23 is screwed onto a portion of the shank of the bolt 22 protruded from the underside of the lobe part, whereby the main clamp body 10 as a whole is toroidally-shaped when viewed from the front side.
As may be viewed from FIG. 1 to FIG. 3, each of the first and second lobe parts 15 includes a pair of sidewall sections 31, an outer end wall section 32 and a seat surface wall section 33. The outer end wall section is straight-shaped (flat) and interconnects the pair of sidewall sections 31 at an extreme outer (remote) end of the lobe part. The seat surface wall section, formed contiguous with both the pair of sidewall sections 31 and the outer end wall section 32, provides a seat surface for the bolt 22 or the nut 23. In addition, a fulcrum part 34, rectangular-shaped when viewed in a plan view, is formed extending from the lower or upper side of the straight-shaped outer end wall section 32 of each of the lobe parts 15. This fulcrum part 34 is formed by ‘bend working’ by a press at the time of press forming of each of the lobe parts 15 of the clamp members.
Referring to FIG. 4 for example, in using the clamp device, a flange 41f of a first piping component 41 and a flange 42f of a second piping component 42 are contacted with each other. In this state, the main clamp body 10 is fitted over outer surface sides of the flange 41f of the first piping component 41 and the flange 42f of the second piping component 42. The nut 23 is then threadedly engaged with the shank of the bolt 22 of the clamp device to be tightened. By so doing, the toroidally-shaped main clamp body 10 is gradually reduced in diameter, with the connecting flanges (41f, 42f) progressively intruding into the insides of the tightening grooves 13 of the main clamp body 10. Concomitantly, there is developed, in the flanges 41, 42, a screw-tightening torque (flange fastening force F) in a direction of strengthening the connection between the two flanges 41, 42 (in the horizontal direction in FIG. 4), thereby tightly clamping the flanges together by the clamp device.